Heat dissipation in hermetically-sealed packaged devices

ABSTRACT

A hermetically sealed package effectively dissipates heat generated inside the package. The hermetically sealed package includes a hermetically sealed enclosure formed from a base portion and a lid. Within the enclosure two or more heat generating elements, such as integrated circuit chips, are supported by the base portion and rise to different heights from the base portion. At least one resilient heat exchange component, such as a leaf spring, extends from the lid of the hermetically sealed enclosure to the different heights. The heat exchange component is configured to conduct heat from the plurality of heat generating elements to the lid of the enclosure.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.14/617,078, filed Feb. 9, 2015, the entirety of which is incorporatedherein by reference.

TECHNICAL FIELD

The present disclosure relates to heat management in packaged devices.

BACKGROUND

Hermetic packaged integrated circuit devices (e.g., in silicon photonicsapplications) are typically used to protect the integrated circuits fromchanging external environmental conditions, and maintain the devicefunctionality. Since hermetic packages are sealed from the outsideenvironment, removing heat generated by the integrated circuits withinthe hermetic package may be challenging.

Hermetic packages offer advantages for the functionality of siliconphotonics packages by ensuring a high level of cleanliness arounddelicate optical interfaces. Silicon photonic packages can generateconsiderable heat during operation, e.g., from a laser diode, theelectronics that control the functionality of the photonics, or othercircuit elements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows components of an enclosure configured for heat transferfrom an integrated circuit to the lid of the enclosure, according to anexample embodiment.

FIG. 1B shows a leaf spring to transfer heat from an integrated circuitto the lid of an enclosure, according to an example embodiment.

FIG. 1C shows a hermetically sealed enclosure with a leaf spring totransfer heat from an integrated circuit to an external heat sinkthrough the lid of the enclosure, according to an example embodiment.

FIG. 2 shows an enclosure with an insulating lid that enables heattransfer through the lid using a leaf spring, according to an exampleembodiment.

FIG. 3 shows an enclosure with an insulating lid that enables heattransfer though the lid using a bed of springs, according to an exampleembodiment.

FIG. 4 shows an enclosure with a plurality of leaf springs configured totransfer heat from a plurality of integrated circuits, according to anexample embodiment

FIG. 5A shows an enclosure with a thermoelectric cooler to assist in thetransfer of heat from a plurality of integrated circuits, according toan example embodiment.

FIG. 5B shows an enclosure with a plurality of thermoelectric coolers toassist in the transfer of heat from a plurality of integrated circuits,according to an example embodiment.

FIG. 6 is a flow diagram illustrating a method of manufacturing ahermetically sealed enclosure that dissipates heat through the lid ofthe enclosure, according to an example embodiment.

DESCRIPTION OF EXAMPLE EMBODIMENTS Overview

An apparatus is provided for effectively dissipating heat generatedinside a hermetically sealed package. The apparatus comprises ahermetically sealed enclosure including a base portion and a lid. Withinthe enclosure a plurality of heat generating elements, such asintegrated circuit chips, are supported by the base portion and rise toa plurality of different heights from the base portion. At least oneresilient heat exchange component, such as a leaf spring, extends fromthe lid of the hermetically sealed enclosure to the plurality ofdifferent heights. The heat exchange component is configured to conductheat from the plurality of heat generating elements to the lid of theenclosure.

Detailed Description

Referring to FIG. 1A, a simplified diagram of a side view of anenclosure 100 is shown. Enclosure 100 comprises a base portion 110 and alid portion 120. Sidewalls may be attached to the base portion 110and/or the lid portion 120. Within the enclosure 100 a heat generatingelement 130 is supported by the base portion 110 and may be secured withan optional layer of adhesive 135. Heat generating element 140 iselectrically connected to heat generating element 130 through electricalconnections 145. A resilient heat exchange component 150 is coupled tothe lid 120 such that when the enclosure 100 is closed and hermeticallysealed, the component 150 makes intimate contact with at least heatgenerating element 140.

In one example, the heat generating element 130 may be an electronicdevice (e.g., a semiconductor integrated circuit) and the heatgenerating element 140 may be an optoelectronic device (e.g., a siliconphotonic device) that is controlled by element 130. Alternatively, thefunctionality of element 130 may be controlled by element 140.Hereinafter, heat generating elements may include and be referred to asintegrated circuits or chips. In another example, additional electricalconnections (e.g., solder bumps, wire bonds, etc.) and/or opticalconnections (e.g., waveguides, gratings, etc.) may be included in theenclosure 100 to allow integrated circuits 130 and/or 140 to communicatewith elements outside of the hermetically sealed enclosure 100.

In a further example, heat exchange component 150 may comprise a leafspring 150 made from a resilient, heat conductive material (e.g.,beryllium copper). The resilient properties of leaf spring 150 allow itto conform to integrated circuit 140 and absorb any process variations,such as height variability in silicon height, solder bump height ofconnection 145, and minor placement variability of integrated circuit140 within the enclosure 100.

Referring now to FIG. 1B, a simplified block diagram of the top view ofleaf spring 150 is shown. Leaf spring 150 comprises a contact surface152 that contacts heat generating elements in the enclosure 100. Thecontact surface 152 is coupled through bridge 154 to the lid surface156. The lid surface 156 is tack-welded to the lid 120 at spots 158. Inone example, the size and geometry of the contact surface 152 and/orbridge 154 may be optimized to balance flexibility and thermalconductivity. In another example, the lid surface may be coupled to thelid 120 without tack welds at spots 158, such as with solder, adhesive,or by press-fitting the lid surface 156 into grooves in the lid 120. Ina further example, the contact surface 152 may act as a heat spreaderfor the integrated circuit 140 to further mitigate localized heatingeffects.

Referring now to FIG. 1C, a simplified diagram of a side view ofenclosure 100 attached to a heat sink 160 is shown. Heat sink 160includes cooling fins 165 to dissipate heat that is generated inside thehermetically sealed enclosure 100. The heat generated from integratedcircuit 140 is conducted through leaf spring 150 and lid 120 to the heatsink 160. In one example, the heat sink 160 is coupled to the lid 120 ofenclosure 100 with a thermally conductive adhesive or solder.

Referring now to FIG. 2, a simplified diagram of an enclosure 100 with athermally insulating lid. Lid 210 is a thermally insulating (e.g.,ceramic or glass) lid to enclosure 100. In order to allow heat frominside the enclosure to reach the top surface of the lid 210efficiently, vias 220 are formed in the lid 210 and filled with athermally conductive material (e.g., metal). The vias 220 are formed toalign with the lid surface 156, such that the heat conducted away withleaf spring 150 reaches one side of the thermally conductive vias 220.The other side of the thermally conductive vias 220 may by coupled to aheat sink 160 (not shown in FIG. 2) to dissipate the heat into theenvironment.

Referring now to FIG. 3, a simplified diagram of an enclosure 100 thattransfers heat using a bed of springs. Bed of springs 310 comprises twothermally conductive surfaces 312 with a plurality of spring elementssandwiched between the two surfaces 312. In FIG. 3, the bed of springs310 is shown coupled to an insulating lid 210 with thermally conductivevias 220. Alternatively, the bed of springs 310 may be coupled to asubstantially metal lid. In one example, the thermally conductivesurfaces 312 are made from a metal such as copper or silver, which mayor may not match the material in vias 220. The lid 210 may have acavity, as shown in FIG. 3, to hold the bed of springs 310.

Referring now to FIG. 4, a simplified diagram of an enclosure 100 withheat generating elements at various different heights is shown. Leafsprings 412, 414, and 416 are tacked at various positions on lid 210such that they can reach different distances into the enclosure 100 whenthe enclosure 100 is sealed. The different distances that leaf springs412, 414, and 416 correspond to the different heights of integratedcircuits/heat generating elements 422, 424, and 426, respectively.Integrated circuit 422 is stacked on top of chip 424, and electricallyconnected through solder bumps 432. Integrated circuits 424 and 426 areelectrically connected to devices outside the enclosure through solderbumps 434 and 436, respectively.

In one example, leaf springs 412, 414, and 416 are all part of onelarger leaf spring 150 that is tacked or bent such that the sectionsreach to different heights corresponding to the heights of the differentintegrated circuits. Vias 220 may be placed in every spot that the leafsprings 412, 414, and 416 attach to the lid 210. In another example, thevarying heights of the leaf springs 412, 414, 416 are configured tominimize the stresses placed on the integrated circuits 422, 424, and426. In a further example, one or more of the leaf springs 412, 414, and416 may be replaced with a bed of springs similar to bed of springs 310shown in FIG. 3.

Referring now to FIG. 5A, a simplified diagram of an enclosure 100 witha thermoelectric cooler is shown. A thermoelectric cooler (TEC) 510 isplaced between the vias 220 and the leaf springs 412, 414, and 416. Inaddition to the thermally conductive vias 220, two electricallyconductive vias 520 and 525 are formed in the insulating lid 210 topower the TEC 510.

In one example, the TEC 510 is a Peltier device that uses electricalpower supplied through the vias 520 and 525 to generate a temperaturedifference between the two sides of the TEC 510. The cold side of theTEC 510 may be placed in contact with the leaf springs 412, 414, and 416to more efficiently remove heat from the chips 422, 424, and 426. Thehot side of the TEC 510 may be placed in contact with the conductivevias 220 to more efficiently transfer heat through the conductive viasto the outside environment.

In another example, the TEC 510 may be used with a metallic lid, such aslid 120 shown in FIGS. 1A-1C, if the TEC 510 is powered from powerchannels in one or more of the enclosed integrated circuits, e.g.,integrated circuits 422, 424, or 426. In a further example, one or moreof the leaf springs 412, 414, or 416 may be replaced by a bed of springssimilar to the bed of springs 310 shown in FIG. 3.

Referring now to FIG. 5B, a simplified diagram of an enclosure withmultiple TECs is shown. In this example, the TEC 532 is disposed betweenthe leaf spring 412 and the integrated circuit 422. The cold side of theTEC 532 makes intimate thermal contact with the integrated circuit 422.The hot side of the TEC 532 is coupled to the leaf spring 412, whichtransfers the heat to metal filled vias 520 and 525 and out of theenclosure. The vias 520 and 525 also provide power to the TEC 532.Similarly, the TEC 534 is disposed between the leaf spring 414 and theintegrated circuit 424, and the TEC 536 is disposed between the leafspring 416 and the integrated circuit 426.

In one example, the TEC 536 is electrically powered through a dedicatedvia 520 (e.g., for negative voltage) and dedicated via 525 (e.g., forpositive voltage), while the TECs 532 and 534 may use the same via 520(e.g. for negative voltage) with dedicated vias 525 (e.g., for positivevoltage). The electrically power delivered to the each TEC 532, 534, and536 may be individually controlled to correspond to the amount of heatthat integrated circuits 422, 424, and 426 generate. In this way eachheat transfer component (e.g., leaf spring 412 and TEC 532, leaf spring414 and TEC 534, etc.) can be optimized for the height of the integratedcircuit and the heat the integrated circuit generates.

Referring now to FIG. 6, a flowchart showing operations in themanufacture of a hermetically sealed enclosure 100 is shown. In step610, a plurality of heat generating devices (e.g., semiconductorintegrated circuits, photonic devices, etc.) are coupled to the base ofthe enclosure. Some of the heat generating devices may be stacked oneach other, and the heat generating devices may come to differentheights above the base portion of the enclosure. In step 620, one ormore heat exchange components, such as leaf springs or bed of springs,are coupled to the lid of the enclosure. The heat exchange componentsare coupled to the lid with a solid thermal contact to enable heat totransfer from the heat exchange component to at least a portion of thelid (e.g., a substantially metallic lid or an insulating lid withmetal-filled vias). Additionally, one or more thermoelectric coolers maybe included in the heat exchange components.

In step 630, the lid is placed on the base portion to enclose the heatgenerating devices, such that the heat exchange components are incontact with the heat generating devices. After the enclosure is closed,and the heat exchange components are in intimate thermal contact withboth the lid of the enclosure and the heat generating devices atdifferent heights, the lid is hermetically sealed to the base portion ofthe enclosure in step 640. In one example, the lid is hermeticallysealed to the base portion by welding, soldering, or brazing techniques.

In summary, the techniques described herein present a hermeticallysealed package that removes heat from functional circuit elements whichemit heat during operations. The package uses a heat exchange component(e.g., a leaf spring) attached to the inside of the lid. The heatexchange component intimately contacts the various devices within thepackage and provides a path for heat transfer away from the devicesthrough the lid of the package. The heat exchange component is resilientand forms an intimate contact to the heat generating elements withoutthermal interface materials (e.g., thermal grease) by self-compensatingfor any height variation which may have been the result of normalprocess variation during assembly. By transferring heat out of thepackage through the lid, the temperature inside the sealed package canbe maintained at temperature below approximately 60° C. and a siliconintegrated circuit stacked on a photonic inside the enclosure can be attemperature below approximately 30° C.

In one form, an apparatus is provided for effectively dissipating heatgenerated inside a hermetically sealed package. The apparatus comprisesa hermetically sealed enclosure including a base portion and a lid.Within the enclosure a plurality of heat generating elements aresupported by the base portion and rise to a plurality of differentheights from the base portion. At least one resilient heat exchangecomponent extends from the lid of the hermetically sealed enclosure tothe plurality of different heights. The heat exchange component isconfigured to conduct heat from the plurality of heat generatingelements to the lid of the enclosure.

In another form, a method for manufacturing a hermetically sealedpackage is provided. The method comprises coupling a plurality of heatgenerating devices to a base portion of an enclosure, such that the heatgenerating devices rise to a plurality of different heights above thebase portion. The enclosure comprises the base portion and a lid. Themethod includes coupling at least one resilient heat exchange componentto the lid of the enclosure. The enclosure is closed by hermeticallysealing the lid to the base portion, such that the resilient heatexchange component comes into thermal contact with the plurality of heatgenerating elements at the plurality of different heights. The resilientheat exchange component transfers heat between the plurality of heatgenerating elements and the lid of the enclosure.

In a further form, an apparatus is provided for transferring heat frominside a hermetically sealed package. The apparatus comprises ahermetically sealed enclosure including a base portion and a lid. Atleast one resilient heat exchange component extends from the lid of thehermetically sealed enclosure to a plurality of different heights fromthe base portion at a plurality of different locations within theenclosure. The heat exchange component is configured to conduct heatfrom inside the enclosure through the lid of the enclosure to outsidethe enclosure.

The above description is intended by way of example only.

What is claimed is:
 1. A method comprising: coupling a plurality of heatgenerating devices to a base portion of an enclosure, the enclosurecomprising the base portion and a lid, wherein the plurality of heatgenerating devices rise to a plurality of different heights above thebase portion; coupling at least one resilient heat exchange component tothe lid of the enclosure; closing the enclosure by hermetically sealingthe lid to the base portion, such that the resilient heat exchangecomponent comes into thermal contact with the plurality of heatgenerating elements at the plurality of different heights and transfersheat between the plurality of heat generating elements and the lid ofthe enclosure.
 2. The method of claim 1, further comprising coupling aheat sink to the lid of the enclosure opposite the resilient heatexchange component.
 3. The method of claim 2, wherein the lid isthermally insulating, and the method further comprises forming thermallyconductive vias through the lid between the resilient heat exchangecomponent and the heat sink.
 4. The method of claim 1, wherein couplingthe resilient heat exchange component to the lid of the enclosurecomprises positioning a thermoelectric cooler between the resilient heatexchange component and the lid of the enclosure.
 5. The method of claim4, further comprising providing electrical power to the thermoelectriccooler through conductive vias in the lid, wherein the lid iselectrically insulating.
 6. The method of claim 1, wherein the at leastone resilient heat exchange component comprises one or more leafsprings, one or more bed of springs, or a combination of one or moreleaf springs and one or more beds of springs.
 7. The method of claim 1,further comprising providing electrical power to the plurality of heatgenerating devices through electrical connections in the base portion ofthe enclosure.
 8. A method comprising: coupling a plurality of resilientheat exchange components to a lid of an enclosure, the enclosurecomprising the lid and a base portion; and closing the enclosure byhermetically sealing the lid to the base portion, such that theplurality of resilient heat exchange components reach a plurality ofdifferent heights from the base portion of the enclosure.
 9. The methodof claim 7, further comprising coupling a heat sink to the lid of theenclosure opposite the plurality of resilient heat exchange components.10. The method of claim 8, wherein the lid is thermally insulating, andthe method further comprises forming thermally conductive vias throughthe lid between the plurality of resilient heat exchange components andthe heat sink.
 11. The method of claim 7, wherein coupling the pluralityof resilient heat exchange components to the lid of the enclosurecomprises positioning a thermoelectric cooler between at least one ofthe resilient heat exchange components and the lid of the enclosure. 12.The method of claim 11, further comprising providing electrical power tothe thermoelectric cooler through conductive vias in the lid, whereinthe lid is electrically insulating.
 13. The method of claim 7, whereinthe plurality of resilient heat exchange components comprises one ormore leaf springs, one or more bed of springs, or a combination of oneor more leaf springs and one or more beds of springs.
 14. The method ofclaim 7, further comprising coupling one or more heat generating devicesto the base portion of the enclosure, wherein the one or more heatgenerating devices rise to the plurality of different heights above thebase portion of the enclosure.
 15. The method of claim 14, furthercomprising providing electrical power to the plurality of heatgenerating devices through electrical connections in the base portion ofthe enclosure.
 16. A system comprising: means for coupling a pluralityof resilient heat exchange components to a lid of an enclosure, theenclosure comprising the lid and a base portion; and means for closingthe enclosure by hermetically sealing the lid to the base portion, suchthat the plurality of resilient heat exchange components reach aplurality of different heights from the base portion of the enclosure.17. The system of claim 16, further comprising means for coupling a heatsink to the lid of the enclosure opposite the plurality of resilientheat exchange components.
 18. The system of claim 17, wherein the lid isthermally insulating, and the system further comprises means for formingthermally conductive vias through the lid between the plurality ofresilient heat exchange components and the heat sink.
 19. The system ofclaim 16, wherein the means for coupling the plurality of resilient heatexchange components to the lid of the enclosure include a thermoelectriccooler positioned between at least one of the resilient heat exchangecomponents and the lid of the enclosure.
 20. The system of claim 19,further comprising conductive vias for providing electrical power to thethermoelectric cooler through the lid, wherein the lid is electricallyinsulating.